Optical member and display device including the same

ABSTRACT

A display device has a backlight unit and a display panel on the backlight unit. The backlight unit has a bottom cover, a light guide plate on the bottom cover, a reflective sheet under the light guide plate, a printed circuit board disposed at one lateral side of the light guide plate, a plurality of light emitting diodes mounted on the printed circuit board, and two or more optical sheets including a wavelength conversion sheet, wherein the wavelength conversion sheet has a lower substrate, an upper substrate on the lower substrate, a wavelength conversion layer between the lower substrate and the upper substrate, a lower anti-reflective layer under the wavelength conversion layer, a lower impact absorbing layer under the lower substrate, and an upper impact absorbing layer on the upper substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. patent applicationSer. No. 14/830,440 filed on Aug. 19, 2015, which is a Continuation ofU.S. patent application Ser. No. 14/111,421 filed on Oct. 11, 2013 (nowU.S. Pat. No. 9,140,837, issued on Sep. 22, 2015), which was filed asPCT International Application No. PCT/KR2011/009235 on Nov. 30, 2011,which claims the benefit of the Patent Korean Application No.10-2011-0034472, filed on Apr. 13, 2011, which are hereby incorporatedby reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

The embodiment relates to an optical member and a device including thesame.

The embodiment relates to an optical member and a display deviceincluding the same.

Recently, flat display devices, such as an LCD (liquid crystal display),a PDP (plasma display panel) and an OLED (organic light emitting diode),have been increasingly developed instead of conventional CRTs (cathoderay tubes).

Among them, the LCD includes a liquid crystal display panel having athin film transistor substrate, a color filter substrate and a liquidcrystal injected between the thin film transistor substrate and thecolor filter substrate. Since the liquid crystal display panel is anon-emissive device, a backlight unit is provided below the thin filmtransistor substrate to supply light. Transmittance of the light emittedfrom the backlight unit is adjusted according to the alignment state ofthe liquid crystal.

The backlight unit is classified into an edge-illumination typebacklight unit and a direct-illumination type backlight unit accordingto the position of a light source. According to the edge-illuminationtype backlight unit, the light source is located at a lateral side of alight guide plate.

The direct-illumination type backlight unit has been mainly developed asthe size of the LCD has become enlarged. According to thedirect-illumination type backlight unit, at least one light source islocated below the liquid crystal display panel to supply the light overthe whole area of the liquid crystal display panel.

When comparing with the edge-illumination type backlight unit, thedirect-illumination type backlight unit can employ a large number oflight sources so that the high brightness can be achieved. In contrast,the direct-illumination type backlight unit must have thickness greaterthan thickness of the edge-illumination type backlight unit in order toensure brightness uniformity.

In order to solve the above problem, a quantum dot bar having aplurality of quantum dots, which can convert blue light into red lightor green light when receiving the blue light, is positioned in front ofa blue LED that emits the blue light. Thus, as the blue light isirradiated onto the quantum dot bar, the blue light, the red light andthe green light are mixed to each other by the quantum dots distributedin the quantum dot bar and the mixed light is incident into the lightguide plate, thereby generating white light.

If the white light is supplied to the light guide plate by using thequantum dot bar, high color reproduction may be realized.

The backlight unit may include an FPCB (flexible printed circuit board)provided at one side of the blue LED, which emits blue light, to supplysignals and power to the LEDs and a bonding member formed under thebottom surface of the FPCB.

The display device capable of displaying various images using the whitelight supplied to the light guide plate through the quantum dot bar asthe blue light is emitted from the blue LED has been extensively used.

SUMMARY OF THE INVENTION

The embodiment provides an optical member having an improved opticalcharacteristic and a display device including the same.

An optical member according to one embodiment includes a wavelengthconversion layer to convert a wavelength of an incident light; and animpact absorbing layer on the wavelength conversion layer.

A display device according to one embodiment includes a light source; aplurality of first optical sheets onto which a light emitted from thelight source is incident; a second optical sheet on the first opticalsheet; and a display panel provided on the second optical sheet, whereinthe second optical sheet comprises: a wavelength conversion layer toconvert a wavelength of the light emitted from the light source; and afirst impact absorbing layer on the wavelength conversion layer.

A display device according to one embodiment includes a light source; awavelength conversion member to convert a wavelength of light emittedfrom the light source; and a display panel on the wavelength conversionmember, wherein the wavelength conversion member comprises: a wavelengthconversion layer including a plurality of wavelength conversionparticles; and an impact absorbing layer on the wavelength conversionlayer.

The embodiment provides an optical member, which can be easilymanufactured and prevent image quality from being degraded due todamage, and a display device including the same.

According to the embodiment, an optical member includes a wavelengthconversion layer to convert a wavelength of an incident light, and animpact absorbing layer on the wavelength conversion layer.

According to the embodiment, a display device includes a light source, aplurality of first optical sheets onto which a light emitted from thelight source is incident, a second optical sheet on the first opticalsheet, and a display panel provided on the second optical sheet. Thesecond optical sheet includes a wavelength conversion layer to convert awavelength of the light emitted from the light source, and a firstimpact absorbing layer on the wavelength conversion layer.

According to the embodiment, a display device includes a light source, awavelength conversion member to convert a wavelength of light emittedfrom the light source, and a display panel on the wavelength conversionmember. The wavelength conversion member includes a wavelengthconversion layer including a plurality of wavelength conversionparticles, and an impact absorbing layer on the wavelength conversionlayer.

As described above, the optical member according to the embodimentincludes an impact absorbing layer. Accordingly, the optical memberaccording to the embodiment can be effectively protected from externalimpact such as scratches.

In particular, if the impact absorbing layer includes acryl resin orurethane resin, the impact absorbing layer represents high scratchresistance, and may have a self-recovery function against the scratches.

In addition, the optical member according to the embodiment includes thewave conversion layer, and the wavelength of the incident light can bechanged.

Therefore, the optical member according to the embodiment changes thewavelength of the light emitted from the light source while protectingother optical sheets. Accordingly, the display device according to theembodiment can be easily manufactured at the less cost, and can berealized in a slimness structure.

In addition, the optical member according to the embodiment may beinterposed between other optical sheets or adjacent to other opticalsheets. Since the optical member according to the embodiment includesthe impact absorbing layer, the optical member is not damaged due to theadjacent optical sheets. In addition, the optical member does not damageadjacent other optical sheets.

Therefore, in the display device according to the embodiment, imagedegradation can be prevented due to the damage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view showing a liquid crystal displayaccording to the embodiment;

FIG. 2 is a perspective view showing a wavelength conversion sheet;

FIG. 3 is a sectional view taken along line A-A′ of FIG. 2;

FIGS. 4 and 5 are sectional views showing various modifications of thewavelength conversion sheet;

FIG. 6 is a view showing a second prism sheet and the wavelengthconversion sheet; and

FIG. 7 is a view showing a procedure in which the wavelength of incidentlight is changed by the wavelength conversion sheet.

DETAILED DESCRIPTION OF THE INVENTION

In the description of the embodiments, it will be understood that when alayer (or film), a region, a pattern, or a structure is referred to asbeing “on” or “under” another substrate, another layer (or film),another region, another pad, or another pattern, it can be “directly” or“indirectly” on the other substrate, layer (or film), region, pad, orpattern, or one or more intervening layers may also be present. Such aposition of the layer has been described with reference to the drawings.The thickness and size of each layer shown in the drawings may beexaggerated, omitted or schematically drawn for the purpose ofconvenience or clarity. In addition, the size of elements does notutterly reflect an actual size.

FIG. 1 is an exploded perspective view showing an LCD (liquid crystaldisplay) according to a first embodiment, and FIG. 2 is a perspectiveview showing a wavelength conversion sheet. FIG. 3 is a sectional viewtaken along line A-A′. FIGS. 4 and 5 are sectional views showing variousdeformations of the wavelength conversion sheet. FIG. 6 is a sectionalview showing a second prism sheet and a wavelength conversion sheet.FIG. 7 is a view showing a procedure of converting the wavelength ofincident light by the wavelength conversion sheet.

Referring to FIGS. 1 to 7, the LCD according to the embodiment includesa backlight unit 10 and a liquid crystal panel 20.

The backlight unit 10 supplies light to the liquid crystal panel 20. Thebacklight unit 10 serves as a surface light source so that the light canbe uniformly supplied to a bottom surface of the liquid crystal panel20.

The backlight unit 10 is disposed below the liquid crystal panel 20. Thebacklight unit 10 includes a bottom cover 100, a light guide plate 200,a reflective sheet 300, a plurality of light emitting diodes 400, aprinted circuit board 401, and a plurality of optical sheets 500.

The upper portion of the bottom cover 100 is open. The bottom cover 100receives the light guide plate 200, the light emitting diodes 400, theprinted circuit board 401, the reflective sheet 300, and the opticalsheets 500 therein.

The light guide plate 200 is disposed in the bottom cover 100 andarranged on the reflective sheet 300. The light guide plate 200 guidesthe light upward by totally-reflecting, refracting and scattering thelight incident thereto from the light emitting diodes 400.

The reflective sheet 300 is disposed below the light guide plate 200. Inmore detail, the reflective sheet 300 is disposed between the lightguide plate 200 and the bottom surface of the bottom cover 100. Thereflective sheet 300 reflects the light upward as the light is outputdownward from the bottom surface of the light guide plate 200.

The light emitting diodes 400 serve as a light source for generating thelight. The light emitting diodes 400 are disposed at one lateral side ofthe light guide plate 200. The light generated from the light emittingdiodes 400 is incident into the light guide plate 200 through thelateral side of the light guide plate 200.

The light emitting diodes 400 may include a blue light emitting diodegenerating the blue light or a UV light emitting diode generating the UVlight. In detail, the light emitting diodes 400 may emit the blue lighthaving the wavelength band of about 430 nm to 470 nm or the UV lighthaving the wavelength band of about 300 nm to 400 nm.

The light emitting diodes 400 are mounted on the printed circuit board401. The light emitting diodes 400 may be disposed under the printedcircuit board 401. The light emitting diodes 400 are driven by receivinga driving signal through the printed circuit board 401.

The printed circuit board 401 is electrically connected to the lightemitting diodes 400. The printed circuit board 401 may mount the lightemitting diodes 400 thereon. The printed circuit board 401 is disposedin the bottom cover 100.

The optical sheets 500 are disposed on the light guide plate 200. Theoptical sheets 500 supplies the light to the liquid crystal panel 20 bychanging or enhancing the optical property of the light output from thetop surface of the light guide plate 200.

The optical sheets 500 may include a diffusion sheet 501, a first prismsheet 502, a second prism sheet 503, and a wavelength conversion sheet504.

The diffusion sheet 501 is provided above the light guide plate 200. Thediffusion sheet 501 improves the uniformity of the passing light. Thediffusion sheet 501 may include a plurality of beads.

The first prism sheet 502 is provided on the diffusion sheet 501. Thesecond prism sheet 503 is provided on the first prism sheet 502. Thefirst prism sheet 502 and the second prism sheet 503 increase thelinearity of light passing through the first prism sheet 502 and thesecond prism sheet 503.

The wavelength conversion sheet 504 is provided on the second prismsheet 503. In more detail, the wavelength conversion sheet 504 may beinterposed between the liquid crystal panel 20 and the second prismsheet 503. The wavelength conversion sheet 504 converts the wavelengthof the incident light so that the incident light can be output upward.

For instance, if the light emitting diodes 400 are blue light emittingdiodes, the wavelength conversion sheet 504 converts the blue lightoutput upward from the light guide plate 200 into the green light andthe red light. In detail, the wavelength conversion sheet 504 converts apart of the blue light into the green light having the wavelength in therange of about 520 nm to about 560 nm, and a part of the blue light intothe red light having the wavelength in the range of about 630 nm toabout 660 nm.

In addition, if the light emitting diodes 400 are UV light emittingdiodes, the wavelength conversion sheet 504 converts the UV light outputfrom the top surface of the light guide plate 200 into the blue light,the green light and the red light. In detail, the wavelength conversionsheet 504 converts a part of the UV light into the blue light having thewavelength in the range of about 430 nm to about 470 nm, a part of theUV light into the green light having the wavelength in the range ofabout 520 nm to about 560 nm, and a part of the UV light into the redlight having the wavelength in the range of about 630 nm to about 660nm.

Therefore, the white light may be generated by the light passing throughthe wavelength conversion sheet 504 without being converted and thelights converted by the wavelength conversion sheet 504. In detail, thewhite light can be incident into the liquid crystal panel 20 through thecombination of the blue light, the green light and the red right. Inother words, the wavelength conversion sheet 504 is an optical member tochange or improve the characteristic of the incident light.

Referring to FIGS. 2 and 3, the wavelength conversion diffusion sheet504 includes a lower substrate 510, an upper substrate 520, a wavelengthconversion layer 530, a lower impact absorbing layer 540, and an upperimpact absorbing layer 550.

The lower substrate 510 is provided under the wavelength conversionlayer 530. The lower substrate 510 may be transparent and flexible. Thelower substrate 510 may adhere to a bottom surface of the wavelengthconversion layer 530.

The lower substrate 510 may include a transparent polymer such aspolyethyleneterephthalate (PET).

The upper substrate 520 is disposed on the wavelength conversion layer530. The upper substrate 520 may be transparent and flexible. The uppersubstrate 520 may adhere to the top surface of the wavelength conversionlayer 530.

The upper substrate 520 may include a transparent polymer such as PET.

The wavelength conversion layer 530 is sandwiched between the upper andlower substrates 520 and 510. The upper and lower substrates 520 and 510support the wavelength conversion layer 530. The upper and lowersubstrates 520 and 510 protect the wavelength conversion layer 530 fromexternal physical impact.

In addition, the upper and lower substrates 520 and 510 have low oxygentransmission rate and low moisture permeability. Thus, the upper andlower substrates 520 and 510 can protect the wavelength conversion layer530 from external chemical penetration, such as oxygen and/or moisture.

The wavelength conversion layer 530 is interposed between the lower andupper substrates 510 and 520. The wavelength conversion layer 530 mayadhere to the top surface of the lower substrate 510, and adhere to thebottom surface of the upper substrate 520.

The wavelength conversion layer 530 includes a plurality of wavelengthconversion particles 531 and a host layer 532.

The wavelength conversion particles 531 are interposed between the lowerand upper substrates 510 and 520. In more detail, the wavelengthconversion particles 531 are uniformly distributed into the host layer532, and the host layer 532 is interposed between the lower substrate510 and the upper substrate 520.

The wavelength conversion particles 531 convert the wavelength of thelight emitted from the light emitting diodes 400. In detail, thewavelength conversion particles 531 receive light emitted from the lightemitting diodes 400 to convert the wavelength of the incident light. Forinstance, the wavelength conversion particles 531 may convert the bluelight emitted from the light emitting diodes 400 into the green lightand the red light. That is, a part of the wavelength conversionparticles 531 may convert the blue light into the green light having thewavelength in the range of about 520 nm to about 560 nm and a part ofthe wavelength conversion particles 531 may convert the blue light intothe red light having the wavelength in the range of about 630 nm toabout 660 nm.

In addition, the wavelength conversion particles 531 may convert the UVlight emitted from the light emitting diodes 400 into the blue light,the green light and the red light. That is, a part of the wavelengthconversion particles 531 may convert the UV light into the blue lighthaving the wavelength in the range of about 430 nm to about 470 nm, anda part of the wavelength conversion particles 531 may convert the UVlight into the green light having the wavelength in the range of about520 nm to about 560 nm. Further, a part of the wavelength conversionparticles 531 converts the UV light into the red light having thewavelength in the range of about 630 nm to about 660 nm.

In other words, if the light emitting diodes 400 are blue light emittingdiodes that emit the blue light, the wavelength conversion particles 531capable of converting the blue light into the green light and the redlight may be employed. In addition, if the light emitting diodes 400 areUV light emitting diodes that emit the UV light, the wavelengthconversion particles 531 capable of converting the UV light into theblue light, the green light and the red light may be employed.

The wavelength conversion particles 531 may include a plurality ofquantum dots. The quantum dots may include core nano-crystals and shellnano-crystals surrounding the core nano-crystals. In addition, thequantum dots may include organic ligands bonded to the shellnano-crystals. In addition, the quantum dots may include an organiccoating layer surrounding the shell nano-crystals.

The shell nano-crystals may be prepared as at least two layers. Theshell nano-crystals are formed on the surface of the core nano-crystals.The quantum dots lengthen the wavelength of the light incident into thecore nano-crystals by using the shell nano-crystals forming a shelllayer, thereby improving the light efficiency.

The quantum dots may include at least one of a group-II compoundsemiconductor, a group-III compound semiconductor, a group-V compoundsemiconductor, and a group-VI compound semiconductor. In more detail,the core nano-crystals may include CdSe, InGaP, CdTe, CdS, ZnSe, ZnTe,ZnS, HgTe or HgS. In addition, the shell nano-crystals may includeCuZnS, CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, HgTe or HgS. The quantum dotmay have a diameter of about 1 nm to about 10 nm.

The wavelength of the light emitted from the quantum dots can beadjusted according to the size of the quantum dot or the molar ratiobetween the molecular cluster compound and the nano-particle precursorin the synthesis process. The organic ligand may include pyridine,mercapto alcohol, thiol, phosphine and phosphine oxide. The organicligand may stabilize the unstable quantum dots after the synthesisprocess. Dangling bonds may be formed at the valence band and thequantum dots may be unstable due to the dangling bonds. However, sinceone end of the organic ligand is the non-bonding state, one end of theorganic ligand is bonded with the dangling bonds, thereby stabilizingthe quantum dots.

In particular, if the size of the quantum dot is smaller than the Bohrradius of an exciton, which consists of an electron and a hole excitedby light and electricity, the quantum confinement effect may occur, sothat the quantum dot may have the discrete energy level. Thus, the sizeof the energy gap is changed. In addition, the charges are confinedwithin the quantum dot, so that the light emitting efficiency can beimproved.

Different from general fluorescent pigments, the fluorescent wavelengthof the quantum dot may vary depending on the size of the particles. Indetail, the light has the shorter wavelength as the size of the particleis reduced, so that the fluorescent light having the wavelength band ofvisible ray can be generated by adjusting the size of the particles. Inaddition, the quantum dot represents the extinction coefficient which is100 to 1000 times higher than that of the general fluorescent pigmentand has the superior quantum yield as compared with the generalfluorescent pigment, so that strong fluorescent light can be generated.

The quantum dots can be synthesized through the chemical wet scheme. Thechemical wet scheme is to grow the particles by immersing the precursormaterial in the organic solvent. According to the chemical wet scheme,the quantum dots can be synthesized.

The host layer 532 surrounds the wavelength conversion particles 531. Inother words, the host layer 532 contains the wavelength conversionparticles 531 uniformly distributed therein. The host layer 532 mayinclude polymer. The host layer 532 is transparent. In other words, thehost layer 532 may include transparent polymer.

The host layer 532 is interposed between the upper and lower substrates520 and 510. The host layer 532 may adhere to the top surface of thelower substrate 510 and the bottom surface of the upper substrate 520.

The lower impact absorbing layer 540 is provided below the wavelengthconversion layer 530. In more detail, the lower impact absorbing layer540 may be disposed below the lower substrate 510. In more detail, thelower impact absorbing layer 540 may be coated on the bottom surface ofthe lower substrate 510.

The lower impact absorbing layer 540 may have elasticity. The lowerimpact absorbing layer 540 may have an elasticity coefficient of about5.8 N/cm² to about 6.6 N/cm². In addition, the lower impact absorbinglayer 540 may have a thickness of about 100 μm to about 500 μm.

When the lower impact absorbing layer 540 has an elasticity coefficientof about 5.8 N/cm² to about 6.6 N/cm², the lower impact absorbing layer540 can be effectively absorb the impact caused by the load of thewavelength conversion sheet 501. In other words, when the lower impactabsorbing layer 540 has the above elasticity coefficient, the lowerimpact absorbing layer 540 absorbs the load of the wavelength conversionsheet 504 so that the lower impact absorbing layer 540 may be properlydeformed.

The lower impact absorbing layer 540 may perform a self-recoveryfunction. Even if a part of the lower impact absorbing layer 540 ispressed due to the external physical impact, the outer appearance of thelower impact absorbing layer 540 may be recovered to the original statethereof.

Therefore, the lower impact absorbing layer 540 can represent highscratch resistance. In addition, the lower impact absorbing layer 540may include acryl resin or urethane resin.

In addition, the lower impact absorbing layer 540 may have a refractiveindex lower than that of the lower substrate 510. In other words, thelower impact absorbing layer 540 optically performs a buffering functionbetween the air layer and the lower substrate 510, reduces reflection,and improves the incidence rate of the light into the lower substrate510.

In order to form the lower impact absorbing layer 540, acryl resincomposition and/or urethane resin composition are coated on the bottomsurface of the lower substrate 510. In this case, in order to coat theresin composition, a spray coating scheme, a dip coating scheme, a spincoating scheme, a slot coating scheme, a slit coating scheme, a barcoating scheme, a roll-to-roll coating scheme can be applied.Thereafter, the coated resin composition is cured by UV light and/orheat, so that the lower impact absorbing layer 540 can be formed.

The upper impact absorbing layer 550 is provided on the wavelengthconversion layer 530. In more detail, the upper impact absorbing layer550 may be provided on the upper substrate 520. In more detail, theupper impact absorbing layer 550 may be coated on the top surface of theupper substrate 520.

The upper impact absorbing layer 550 may have elasticity. The upperimpact absorbing layer 550 may have an elasticity coefficient of about5.8 N/cm² to about 6.6 N/cm². In addition, the upper impact absorbinglayer 550 may have a thickness of about 100 μm to about 500 μm.

When the upper impact absorbing layer 550 has an elasticity coefficientof about 5.8 N/cm² to about 6.6 N/cm², the upper impact absorbing layer550 can be effectively absorb the impact caused by the load of theliquid crystal panel 20. In other words, when the upper impact absorbinglayer 550 has the above elasticity coefficient, the upper impactabsorbing layer 550 absorbs the load of the liquid crystal panel 20 sothat the upper impact absorbing layer 550 may be properly deformed.

The upper impact absorbing layer 550 may perform a self-recoveryfunction. Even if a part of the upper impact absorbing layer 550 ispressed due to the external physical impact, the outer appearance of theupper impact absorbing layer 550 may be recovered to the original statethereof.

Therefore, the upper impact absorbing layer 550 can represent highscratch resistance. In addition, the upper impact absorbing layer 550may include acryl resin or urethane resin.

In order to form the upper impact absorbing layer 550, acryl resincomposition and/or urethane resin composition are coated on the bottomsurface of the upper substrate 520. Thereafter, the coated resincomposition is cured by UV light and/or heat, so that the upper impactabsorbing layer 550 can be formed.

The lower impact absorbing layer 540 is coated on the bottom surface ofthe lower substrate 510. In addition, the upper impact absorbing layer550 is coated on the top surface of the upper substrate 520. Therefore,the lower impact absorbing layer 540 can improve the sealing property ofthe lower substrate 510. In addition, the upper impact absorbing layer550 can improve the sealing property of the upper substrate 520.

Therefore, the lower impact absorbing layer 540 and the upper impactabsorbing layer 550 can easily prevent the wavelength conversionparticles 531 contained in the wavelength conversion layer 530 frombeing deformed due to external moisture and/or external oxygen.

In addition, the lower impact absorbing layer 540 may have a refractiveindex lower than that of the lower substrate 510. In addition, the upperimpact absorbing layer 550 may have a refractive index lower than thatof the upper substrate 520.

Therefore, the lower and upper impact absorbing layers 540 and 550improve the incidence of external light, and can act as ananti-reflective layer to prevent the light from being reflected to theoutside.

As shown in FIG. 4, the lower impact absorbing layer 540 may be directlyprovided on the bottom surface of the wavelength conversion layer 530.In other words, the lower impact absorbing layer 540 may be directlycoated on the bottom surface of the wavelength conversion layer 530.

The upper impact absorbing layer 550 may be directly provided on the topsurface of the wavelength conversion layer 530. In other words, theupper impact absorbing layer 550 may be directly coated on the topsurface of the wavelength conversion layer 530.

In addition, as shown in FIG. 5, a lower anti-reflective layer 560 maybe formed on the bottom surface of the lower substrate 510. In addition,the lower impact absorbing layer 540 may be directly coated on thebottom surface of the lower anti-reflective layer 560.

An upper anti-reflective layer 570 may be formed on the top surface ofthe substrate 520. The upper impact absorbing layer 550 may be directlycoated on the top surface of the upper anti-reflective layer 570.

The lower and upper anti-reflective layers 560 and 570 can serve as ananti-reflective function. The lower anti-reflective layer 560 may have arefractive index lower than that of the lower substrate 510, and theupper anti-reflective layer 570 may have a refractive index lower thanthat of the upper substrate 520.

The refractive index of the lower impact absorbing layer 540 may belower than that of the lower anti-reflective layer 560. The refractiveindex of the upper impact absorbing layer 550 may be lower than that ofthe upper anti-reflective layer 570.

Therefore, the light can be effectively incident onto the wavelengthconversion layer 530 by the lower and upper impact absorbing layers 540and 550 as well as the lower and upper anti-reflective layers 560 and570.

The liquid crystal panel 20 is disposed on the optical sheets 500. Inaddition, the liquid crystal panel 20 is disposed on the panel guide 23.The liquid crystal panel 20 is guided by the panel guide 23.

The liquid crystal panel 20 displays images by adjusting intensity oflight passing through the liquid crystal panel 20. In detail, the liquidcrystal panel 20 is a display panel for displaying the images by usingthe light emitted from the backlight unit 10. The liquid crystal panel20 includes a TFT substrate 21, a color filter substrate 22 and a liquidcrystal layer interposed between the two substrates. In addition, theliquid crystal panel 20 includes polarizing filters.

Hereinafter, the TFT substrate 21 and the color filter substrate 22 willbe described in detail although it is not shown in the drawings indetail. The TFT substrate 21 includes a plurality of gate lines and aplurality of data lines crossing the gate lines to form pixels and athin film transistor (TFT) is provided at each cross section such thatthe thin film transistor TFT can be connected to a pixel electrode ofthe pixel in one-to-one correspondence. The color filter substrate 22includes color filters having R, G and B colors corresponding to thepixels, a black matrix covering the gate lines, data lines and thin filmtransistors within the limit of the color filters, and a commonelectrode covering the above elements.

A driving PCB 25 is provided at an outer peripheral portion of the LCDpanel 21 to supply driving signals to the gate lines and data lines.

The driving PCB 25 is electrically connected to the liquid crystal panel20 by a COF (chip on film) 24. The COF 24 may be replaced with a TCP(tape carrier package).

The wavelength conversion sheet 504 may be provided on the uppermostportion of the optical sheets 500. In other words, the wavelengthconversion sheet 504 can cover other optical sheets 500. Therefore, thewavelength conversion sheet 504 can protect other optical sheets 500.

In detail, the bottom cover 100 receives therein the light guide plate200, the reflective sheet 300, the light emitting diodes 400, theprinted circuit board 401, and the optical sheets 500 without thewavelength conversion sheet 504. Thereafter, the wavelength conversionsheet 504 is stacked on the optical sheets 500, so that the assembly ofthe backlight unit 10 is completed.

Thereafter, when the liquid crystal panel is assembled, the backlightunit 10 may be transferred. In this case, since the wavelengthconversion sheet 504 includes the upper impact absorbing layer 550, thewavelength conversion sheet 504 can protect other optical sheets 501,502, and 503 while minimizing the damage of the wavelength conversionsheet 504.

In addition, as shown in FIG. 6, the second prism sheet 503 is providedon the top surface thereof with a plurality of protrusion patterns 580having a pyramid shape. The protrusion pattern 580 may directly makecontact with the bottom surface of the wavelength conversion sheet 504.

Thereafter, since the wavelength conversion sheet 504 includes the lowerimpact absorbing layer 540, the wavelength conversion sheet 504 canminimize the damage caused by the protrusion pattern 580. Therefore, theliquid crystal display according to the embodiment can minimize damagescaused by external and internal physical impacts. Therefore, the liquidcrystal display according to the embodiment can minimize the degradationof image quality caused by scratches.

In addition, the wavelength conversion sheet 504 includesanti-reflection layers at both upper and lower portions thereof.Therefore, as shown in FIG. 7, the light passing through the wavelengthconversion layer 530 without being changed can be reflected downward bythe liquid crystal panel 20. In this case, the light reflected downwardcan be effectively incident onto the wavelength conversion layer 530 bythe upper impact absorbing layer 550 and/or the upper anti-reflectivelayer 570.

As described above, since a greater amount of light is incident onto thewavelength conversion layer 530, the conversion efficiency of thewavelength conversion layer 530 can be more improved.

Therefore, the wavelength conversion sheet 504 effectively converts thewavelength of the light output from the light emitting diodes 400, andthe liquid crystal display according to the embodiment can represent theimproved color reproduction and brightness.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effects such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

The LCD according to the embodiments can be used in the display field.

What is claimed is:
 1. A display device comprising: a backlight unit;and a display panel on the backlight unit, wherein the backlight unitcomprises: a bottom cover; a light guide plate on the bottom cover; areflective sheet under the light guide plate; a printed circuit boarddisposed at one lateral side of the light guide plate; a plurality oflight emitting diodes mounted on the printed circuit board; and two ormore optical sheets including a wavelength conversion sheet; wherein thewavelength conversion sheet comprises: a lower substrate; an uppersubstrate on the lower substrate; a wavelength conversion layer betweenthe lower substrate and the upper substrate; a lower anti-reflectivelayer under the wavelength conversion layer; an upper anti-reflectivelayer on the wavelength conversion layer; a lower impact absorbing layerunder the lower substrate; and an upper impact absorbing layer on theupper substrate, wherein the lower substrate is disposed under thewavelength conversion layer, wherein the lower substrate is transparent,wherein the lower substrate includes polyethyleneterephthalate (PET),wherein the upper substrate is disposed on the wavelength conversionlayer, wherein the upper substrate includes polyethyleneterephthalate(PET), wherein the lower anti-reflective layer has a refractive indexlower than a refractive index of the lower substrate, wherein the upperanti-reflective layer has a refractive index lower than a refractiveindex of the upper substrate, and wherein the wavelength conversionlayer is sandwiched between the lower substrate and the upper substrate,wherein the wavelength conversion layer comprises: a host layer; and aplurality of wavelength conversion particles in the host, wherein thehost layer is disposed between the lower substrate and the uppersubstrate, wherein the lower impact absorbing layer is disposed underthe wavelength conversion layer, wherein the upper impact absorbinglayer is disposed on the wavelength conversion layer, wherein the loweranti-reflective layers extend from one end of the lower substrate to theother end of the lower substrate, and wherein the upper anti-reflectivelayers extend from one end of the upper substrate to the other end ofthe upper substrate.
 2. A backlight unit comprising: a bottom cover; alight guide plate on the bottom cover; a reflective sheet under thelight guide plate; a printed circuit board disposed at one lateral sideof the light guide plate; a plurality of light emitting diodes mountedon the printed circuit board; and two or more optical sheets on thelight guide plate, wherein the wavelength conversion sheet comprises: alower substrate; an upper substrate on the lower substrate; a wavelengthconversion layer between the lower substrate and the upper substrate; alower anti-reflective layer under the wavelength conversion layer; anupper anti-reflective layer on the wavelength conversion layer; a lowerimpact absorbing layer under the lower substrate; and an upper impactabsorbing layer on the upper substrate, wherein the lower substrate isdisposed under the wavelength conversion layer, wherein the lowersubstrate is transparent, wherein the lower substrate includespolyethyleneterephthalate (PET), wherein the upper substrate is disposedon the wavelength conversion layer, wherein the upper substrate includespolyethyleneterephthalate (PET), wherein the lower anti-reflective layerhas a refractive index lower than a refractive index of the lowersubstrate, wherein the upper anti-reflective layer has a refractiveindex lower than a refractive index of the upper substrate, and whereinthe wavelength conversion layer is sandwiched between the lowersubstrate and the upper substrate, wherein the wavelength conversionlayer comprises: a host layer; and a plurality of wavelength conversionparticles in the host, wherein the host layer is disposed between thelower substrate and the upper substrate, wherein the lower impactabsorbing layer is disposed under the wavelength conversion layer,wherein the upper impact absorbing layer is disposed on the wavelengthconversion layer, wherein the lower anti-reflective layers extend fromone end of the lower substrate to the other end of the lower substrate,and wherein the upper anti-reflective layers extend from one end of theupper substrate to the other end of the upper substrate.
 3. Thebacklight unit of claim 2, wherein an upper portion of the bottom coveris open, and wherein the bottom cover receives the light guide plate,the light emitting diodes, the printed circuit board, the reflectivesheet, and the optical sheets.
 4. The backlight unit of claim 2, whereinthe light guide plate is disposed in the bottom cover, wherein the lightguide plate is disposed on the reflective sheet, and wherein the lightguide plate guides the light upward by totally-reflecting, refractingand scattering the light incident thereto from the light emittingdiodes.
 5. The backlight unit of claim 2, wherein the reflective sheetis disposed under the light guide plate, wherein the reflective sheet isdisposed between the light guide plate and the bottom surface of thebottom cover, and wherein the reflective sheet reflects the light upwardas the light is output downward from the bottom surface of the lightguide plate.
 6. The backlight unit of claim 2, wherein the lightemitting diodes include a blue light emitting diode or UV light emittingdiode, wherein the light emitting diodes are disposed at one lateralside of the light guide plate, and wherein the light generated from thelight emitting diodes is incident into the light guide plate through thelateral side of the light guide plate.
 7. The backlight unit of claim 2,wherein the printed circuit board is electrically connected to the lightemitting diodes, and wherein the printed circuit board is disposed inthe bottom cover.
 8. The backlight unit of claim 2, wherein the opticalsheets are disposed on the light guide plate, and wherein the opticalsheets supplies the light to a display panel by changing or enhancingthe optical property of the light output from the top surface of thelight guide plate.
 9. The backlight unit of claim 2, wherein the opticalsheets include at least two sheet of a diffusion sheet, a first prismsheet, a second prism sheet, and a wavelength conversion sheet.
 10. Awavelength conversion sheet comprising: a lower substrate; an uppersubstrate on the lower substrate; a wavelength conversion layer betweenthe lower substrate and the upper substrate; a lower anti-reflectivelayer under the wavelength conversion layer; an upper anti-reflectivelayer on the wavelength conversion layer; a lower impact absorbing layerunder the lower substrate; and an upper impact absorbing layer on theupper substrate, wherein the lower substrate is disposed under thewavelength conversion layer, wherein the lower substrate is transparent,wherein the lower substrate includes polyethyleneterephthalate (PET),wherein the upper substrate is disposed on the wavelength conversionlayer, wherein the upper substrate includes polyethyleneterephthalate(PET), wherein the lower anti-reflective layer has a refractive indexlower than a refractive index of the lower substrate, wherein the upperanti-reflective layer has a refractive index lower than a refractiveindex of the upper substrate, and wherein the wavelength conversionlayer is sandwiched between the lower substrate and the upper substrate,wherein the wavelength conversion layer comprises: a host layer; and aplurality of wavelength conversion particles in the host, wherein thehost layer is disposed between the lower substrate and the uppersubstrate, wherein the lower impact absorbing layer is disposed underthe wavelength conversion layer, wherein the upper impact absorbinglayer is disposed on the wavelength conversion layer, wherein the loweranti-reflective layers extend from one end of the lower substrate to theother end of the lower substrate, and wherein the upper anti-reflectivelayers extend from one end of the upper substrate to the other end ofthe upper substrate.
 11. The wavelength conversion sheet of claim 10,wherein the upper substrate and the lower substrate are flexible. 12.The wavelength conversion sheet of claim 10, wherein the lower substratesupports the wavelength conversion layer.
 13. The wavelength conversionsheet of claim 10, wherein the host layer includes a transparentpolymer.
 14. The wavelength conversion sheet of claim 10, wherein thelower impact absorbing layer is directly disposed under the lowersubstrate.
 15. The wavelength conversion sheet of claim 10, wherein theupper impact absorbing layer is directly disposed on the uppersubstrate.